Why not try something simple like putting an x in from to the name of that folder. Hopefully the installer will ignore it as it will not recognise the name. This is assuming windows allows you to rename the folder. You might be able to rename the actual file, which is probably better but you may not be allowed to do it if the file has been corrupted. Try it though.
Then try installing iTunes.
If you haven't already, download and save the iTunessetup file on your PC and run it from there.
http://www.apple.com/itunes/download/